Carbon nanotubes (hereinafter, referred as to “CNTs”) are understood to mean cylindrical carbon nanotubes having a diameter of 3 to 150 nm, preferably 3 to 100 nm, and a length of many times, i.e. at least 100 times the diameter. CNTs consist of aligned carbon atom layers and have different types of cores. CNTs are also called as carbon fibrils or hollow carbon fibers. CNTs are industrially essential in the production of composites because of the size and specific properties thereof and may be utilized in further applications including electrical applications and energy applications.
CNTs are generally manufactured by arc discharge, laser ablation, chemical vapor deposition or the like. However, arc discharge and laser ablation are disadvantageously not suited to mass-production and involve excessive preparation costs or laser purchase costs.
Furthermore, chemical vapor deposition has problems in that synthesis velocity is very low and synthesized CNT particles are extremely small in the case of using a gas-phase dispersion catalyst and has a limit to bulk production of CNTs because space utilization inside a reactor is significantly reduced in the case of using a substrate-supported catalyst.
The catalytically active component of the catalyst generally has an oxide form, a partially or completely reduced form, or a hydroxide form and the catalyst may be a supported catalyst, a co-precipitation catalyst or the like which is commonly used for the production of CNTs. Of these, the supported catalyst is preferred because the carbon nanotube catalyst advantageously has a higher bulk density than a co-precipitation catalyst, reduces probability of generation of fine powder by attrition which may be generated during fluidization due to small-amount generation of fine powder of 10 microns or less unlike the co-precipitation catalyst, and enables stable operation of the reactor due to superior mechanical strength of the catalyst.
In addition, as a method for producing a supported catalyst, an impregnation method including mixing an aqueous metal solution and a support, followed by coating and drying is suggested. When a catalyst is produced using a rotary evaporator or the like at room temperature to a medium to low temperature of about 60° C., CNT yield and amount of supported metal can be increased, but a problem such as deterioration in activity based on amount of the supported metal is generated due to high viscosity of the homogeneous metal solution.
Accordingly, there is a need for research on methods for manufacturing supported catalysts capable of solving this problem.